The present invention is concerned with a building panel constructed in layers with good elastomechanical and fire-proof technological characteristics, preferably for use as a double or multiple floor for equipping computer rooms, and with a process of manufacturing it.
The trend for simple construction which may be observed in the building and construction industry is followed by a better technical and economic use of material, especially of the composite construction type, which is increasingly becoming of importance. The main advantage is that different material characteristics, which would not otherwise be combined, are united in one construction element. The most favorable characteristics can be formed for certain areas of use by the corresponding choice of single construction components. If, for example, the tractive force and the fire-resistance are considered, then combined favorable material characteristics can be obtained by means of a combination of pure gypsum with glass fibres in mat form. Such a combination occurs in a process which is already known where glass fibres in mat or textile form in regular distribution are immersed in a wet process in amounts of up to 10 mass-% in pure gypsum, whereby the elastomechanic properties of the pure gypsum panel can be improved by a combination with glass fibres.
The technological development went further to multiple layer panels where each layer was responsible for a part of the function to be fulfilled by the entire panel. There are three separate ways of manufacturing such panels:
Combinations where the layers are bound to one another by means of an adhesive;
Combinations where the layers are held together by constructive connection members;
Combinations where the layers are stuck together by means of construction characteristic adhesion forces.
Adhesive connections display disadvantages due to the embrittlement caused by aging and due to the requirements of joint fitting which could have an effect on the bearing construction parts. In the second process, single pre-prepared layers are screwed together or bound together in some other way. In practice the third connection is preferred.
It is known from DD-PS 47099 that the swelling forces, which take effect in the course of the hydration in glass fibre reinforced gypsum covering layers, can be used for connection with other materials. The principle is based on the fact that liquid to plastic gypsum covering layers, due to their having swollen, shrink in dove-tail shaped angled metal fitting frames. Metal and glass reinforced gypsum combine statically whereby the metal frame also takes over the edge protection. If a supporting core, for example honeycomb or lattice-work constructions, is pressed so deeply into the binding means mixture (in flowing state) of the covering layer that it can have contact with the gypsum, then a connection between these can be obtained. A supporting means layer, pressed so far into a binding means which is in a flowing state that adhesive strength is produced between both layers in the hardened state, is therefore usually used in the manufacturing of multiple layer panels. According to this procedure it is also already known that a gypsum milk-glass fibre layer can be put onto a sheet form and a flake-board then pressed into the gypsum-glass fibre layer which is still in a flowable state. In order to improve the adhesion between the gypsum and the flake-board layer, the upper layer of the flake-board is pre-roughened with coarse sandpaper or is provided with grooves.
In spite of this improvement, the connection between the gypsum layer and the flake-board is still unsatisfactory in that the multiple layer panel tends to lose adhesion at the bordering surface between the flake-board and the gypsum layer. In particular with a conceivable use of a gypsum-glass fibre layer as an intermediate layer, there is a danger that, as a result of the low adhesion characteristic of the gypsum layer, the flake-board layers will no longer adhere to one another if there is a strong elastomechanic requirement.